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Soy and Declining Sperm Counts

Soy and Declining Sperm Counts

We have heard that soy can have an effect on female fertility, but can soy affect male fertility also? Researchers at the Harvard School for Public Health in Boston say so.

In a study released by the School, it was reported that those who eat just a half a serving of soy per day may have a 40% decrease in sperm production. That can have a devastating effect on men who already suffer with lower-than-normal sperm production.

So, what is the problem with soy – something that is generally touted as being very healthy for you? It contains isoflavones, which contain phytoestrogens, or estrogen-like substances that can confuse the body and make it think there is too much estrogen in the system. This is what causes a decrease in sperm production, even affecting sperm quality. Basically, the report explains, soy causes interference with hormone signals and this can decrease both male and female fertility.

For instance, the six-year Harvard study indicated that men who ate just a half serving of soy only released 65 million sperm in their semen, compared to non-soy-eating participants who averaged 120 million sperm per sample. T That is a dramatic decrease that cannot be overlooked, say the experts. Still others disagree, saying that even 65 million sperm are enough to impregnate a partner. That is true, but, say critics, what about men who already have a decreased sperm production level? Cutting their sperm production by another 40-50% could make them totally infertile.

Some researchers have gone so far as to say that soy is “feminizing” today’s male, although many disagree, stating that an increase in this estrogen-mimicking chemical may affect sperm counts, but nothing else in regards to their “maleness.”

Women too can be affected by soy products, since it can boost their estrogen levels even higher, playing havoc with other fertility hormones in the body. Ovulation and conception require a balance of hormones in the body at certain times of the month, and having too much estrogen can throw off the entire process.

Now, if you are not a vegetarian nor do not often eat soy products, you may think that you are safe from this fertility-killer. Not necessarily. Soy is hidden in a lot of our foods without us ever realizing it. For instance, most power drinks, protein powders, breads, power bars, nutritional bars and other foodstuffs contain high levels of soy. Drinking just a few ounces of one of these soy-based drinks every day could have a detrimental effect on both you and your partner’s overall ability to conceive a child and should be considered.

Another thing to consider is that most soy grown in the USA is genetically modified; GMO foods have also been shown to have negative effects on fertility.

For those who have been trying to get pregnant to no avail, a good look at both of your soy levels could be the answer. The good news is that soy does not seem to cause any lasting fertility damage. Luckily, by taking the soy out of your diet, you can boost sperm levels within a few months, making a pregnancy more likely.


  • Chavarro, J., Toth, T., Sadio, S., and Hauser, R. (Nov. 2008). Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Hum. Reprod. DOI: 10.1093/humrep/den243 Retrieved from:

Dr. Christine Traxler M.D., OB/GYN
Dr. Christine Traxler M.D., OB/GYN

Dr. Traxler is a University-trained obstetrician/gynecologist, working with patients in Minnesota for over 20 years. She is a professional medical writer; having authored multiple books on pregnancy and childbirth; textbooks and coursework for medical students and other healthcare providers; and has written over 1000 articles on medical, health, and wellness topics.  Dr. Traxler attended the University of Minnesota College of Biological Sciences and University of Minnesota Medical School,  earning a degree in biochemistry with summa cum laude honors in 1981,  and receiving her Medical Doctorate degree (MD) in 1986.

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  1. Avatar

    Soy beans have always considered to be a healthy food in Asia and had never been giving an infertility problem for thousands of years. Now that soy is the problem. Can it be because it is genetic modified?

    • Dear Lai Yin,

      Yes, this is in part why, but also that rather than consume soy whole or fermented soy, people have begun over-consuming processed spy foods that also contain preservatives, added sugars, fillers, binders, etc.

  2. Avatar

    I love learning about natural remedies and the powerful effects of herbs.

  3. Avatar

    Can you provide the source for the Harvard School of Public Health research that supports “In a study released by the School, it was reported that those who eat just a half a serving of soy per day may have a 40% decrease in sperm production. That can have a devastating effect on men who already suffer with lower-than-normal sperm production,” please?

  4. Avatar

    Good day!

    Thanks a lot ma’am Willett for your great reply. I really appreciated your message. And I’m aware now the things to be considered for my good.

    If I will order your product how would I pay it? I’m from Philippines.

    Best regards,


  5. Avatar

    Hi ma’am! I had also low sperm counts so please give me an exact advice coz I bought today Vitamin E 400 IU from soybean oil if is this also not good for me?


    • Elizabeth Willett, MA, CH

      Hello Edlin!

      Vitamin E has been shown to increase sperm health and motility. We feel it first and foremost to eat a wholefood diet filled with foods that provide Vitamin E. Some of these foods are: Raw vegetable oils, nuts, nut butters, rice bran oil, barley, seaweed, green leafy vegetables, asparagus, avocado, berries, and tomatoes.

      Vitamin E from soybean oil may not be the best because the soy may be GMO soy and the soybeans were also very likely to have been highly processed in order to extract the oil. You can learn about the forms of Vitamin E and what to look for when purchasng a Vitamin E supplement in this article: .

      We have the Male Factor Formula Kit if you are interested in supplements to support sperm health, count, motility and morphology.

      Best Wishes!

  6. Update 2014 – We are back! We have been away for a while and we sure have missed all of your wonderful questions and thoughts on our articles. Moving forward, one of our staff herbalists will be here to respond to comments! We look forward to connecting with our readers once again!

  7. Avatar

    Hi there,

    Thanks for all the great information. Just wondering if you know if this study refers to all soy products including non-GMO fermented soy as well or just unfermented soy products???


    • Hi Jodi,

      It even refers to fermented soy products such as miso, tempeh and soy sauce. Bummer 🙁 So that means all soy, not so good!

      Sorry to be a bummer.

      Have a great day.